The present invention relates to a printed circuit board and a flip chip package using the same, and more particularly to a printed circuit board with improved reliability in the bump joints and a flip chip package using the same.
Recently, the electronic industry has adopted a mounting technique employing a printed circuit board, which enables the high-density and high-precision mounting of parts for the purpose of miniaturizing and decreasing the weight of electronic appliances. Specifically, with the development of technologies associated with chip size package (CSP), such as a ball grid array (BGA) package and a tape carrier package (TCP), a high-density printed circuit board capable of mounting an increased number of semiconductor chips has drawn considerable attention.
Accordingly, the manufacture of light-weight and compact electronic appliances requires fine-processing techniques as well as the printed circuit boards conducive to the high-density mounting of parts.
A printed circuit board is made by forming line patterns on an insulation layer using a conductive material, such as copper, and it is the substrate on which the electronic parts are mounted thereon. A printed circuit board has an insulation layer, metal lines formed on the upper and lower surfaces of the insulation layer, and via metal lines formed through the insulation layer to electrically connect the metal lines.
Printed circuit boards may be used in flip chip packages. In a flip chip package, securing high reliability of the bump joints electrically connecting the semiconductor chip and the printed circuit board is important.
However, during a fabrication process, the solder resist formed on the metal lines versus the solder resist formed on other areas of the printed circuit board but not on the metal lines creates difference in bulk such that these two regions on the printed circuit board would have different thermal expansion coefficients. The difference in the thermal expansion coefficient in theses portions on the printed circuit board causes the stress to increase in the boundaries of the metal line on the printed circuit board. Consequently, when manufacturing a flip chip package incorporating a conventional printed circuit board as discussed above, adverse influence is exerted on the bump joints that are connected to metal lines such that cracks may occur in the bump joints. This degrades the reliability of the flip chip package.
Also, the difference in thermal expansion coefficient induced by the difference in bulk between the portions of the solder resist on the printed circuit board formed on the metal lines versus not on the metal line also causes an increase in the overall stress on the printed circuit board, thereby causing warpage in the printed circuit board.